Concentric combustion system with cooled dividing partition



April 11, 1961 s. R. PUFFER 2,978,868

CONCENTRIC- COMBUSTION SYSTEM WITH COOLED DIVIDING PARTITION Filed Dec.21, 1959 INVENTOR. 5.444051 E PflFF-E United States Patent CONCENTRICCOMBUSTION SYSTEM WITH COOLED DIVIDING PARTITION Samuel R. Puffer,Hartland, Vt., assignor to General Electric Company, a corporation ofNew York Filed Dec. 21, 1959, Ser. No. 861,075

7 Claims. (CI. 60-356) This invention relates to concentric combustionsystems of the kind in which a central combustion passage is surroundedby an annular supplementary combustion passage, these passages beingseparated by an annular dividing partition. Systems of this kind findtheir principal application in those jet propulsion engines of thebypass or ducted fan type in which afterburners are provided in both amain propulsion conduit and a bypass conduit.

A principal problem in such a system is the cooling of the annulardividing partition, which is subjected to high temperatures ofcombustion both internally and externally. It is an object of myinvention to provide a concentric combustion system having improvedmeans for cooling a dividing partition thereof. It is a further objectof my invention to provide a concentric combustion system having animproved dividing partition, which is cooled by vaporization of fuel andwhich aflords improved means for injection of fuel into concentriccombustion passages of the system.

Further objects and advantages of my invention will become apparent asthe following description proceeds.

Briefly stated, in accordance with one aspect of my invention, I providea concentric combustiousystem withan annular dividing partition havinginner and outer radially spaced walls to enclose an annularfuel-vaporizing chamber, and form a plurality of fuel injection orificesspaced along both the inner and outer walls of the dividing partition. Ifurther provide means for supplying streams of fuel into thefuel-vaporizing chamber. By these means, fuel is vaporized in thechamber for cooling of the internal wall surfaces. A mixture ofvaporized fuel is injected through the orifices in both walls toinstitute combustion in the central and supplementary combustionpassages, sweeping the outer surfaces of the'walls toprovide furthercooling of the dividing partition. The partition is thus cooledinternally and externally, and

protected from the high temperatures of combustion in the concentriccombustion passages; also, vaporized fuel is injected into thecombustion passages in a series of streams spaced along the partition,so that combustion occurs with evenly increasing intensity as itproceeds downstream.

In a preferred embodiment of my invention, 1 divide the fuel-vaporizingchamber into concentric annular portions by means of an annular baflleradially spaced between the walls of the partition. By these means,pressure differentials existing between the concentric combustionpassages are prevented from interfering with the desired division offuel flow between them, or starving one of the passages. However, theuse of the annular bafile is not essential to the practice of myinvention.

In an alternative embodiment of my invention, I form openings betweenupstream ends of the walls to admit streams of diluent fluid into thefuel-vaporizing chamber, to assist in complete evaporation of the fuelstreams.

: The diluent fluid is drawn from that one of the central orsupplementary combustion passages in which the higher pressure exists,so that reverse flow is avoided. However, the temperature of the diluentfluid must not be sufliciently high to produce ignition within thefuelvaporizing chamber.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which I regard as myinvention, it is believed that the invention will be better understoodfrom the following detailed description thereof, taken in connectionwith the accompanying drawing, in which:

Fig. l is an elevation view, partially in section, of one embodimentofmy improved combustion system as applied to a jet propulsion engine;

Fig. 2 is a pictorial view of a fragmentary portion of the combustionsystem; n

Fig. 3 is a pictorial view of a fragmentary portion of a modifiedembodiment of the combustion system; and

Fig. 4 is an elevation, partially in section, of a further modificationof the combustion system as applied to a jet propulsion engine.

Referring to Fig. 1, my improved concentric combustion system is shownin operative relation to a conventional' bypass jet propulsion enginegenerally designated l. The engine is of the bypass or ducted fan type,illustrating one of the uses to which the system can be adapted. Engine1 includes concentric annular main and bypass fluid conduits 2 and 3,respectively, which are formed by concentric annular casings 5 and 6.Each of the conduits receives working fluid, ordinarily atmospheric air,in streams flowing in the direction shown by the arrows. A compressor(not shown) is rotatably mounted upstream in conduit 2 for compressionof the working fluid, and is drivingly connected to a turbine 7 by meansof a shaft 8. A fuel combustor 9 of well-known type injects and ignitesfuel in the working fluid stream, from which energy is extracted byturbine 7 to drive the compressor. In the bypass engine shown, anadditional turbine 10 receives working fluid exhausted from turbine 7,extracting further energy therefrom to drive a fan 11 in conduit 3. Asshown, the blades'of fan 11 are directly mounted upon a shroud ring 12attached to the buckets of turbine 10. Fan 11 operates in a well knownmanner to accelerate the flow of working fluid in conduit 3, foraugmentation of the thrust produced by working fluid exhausted fromconduit 2.

An annular exhaust collector duct 13 of substantial axial length isprovided to accommodate reheat or afterburning combustion in the workingfluid streams exhausted from engine 1. A flange 14 is formed on anupstream end of duct 13, and is secured to a mating flange 15 of casing6 by means of a circumferential row of fasteners 16. At its downstreamend, duct 13 is formed with an exhaust nozzle 17 for discharge of theworking fluid streams to generate propulsive thrust.

Duct 13 also serves to support turbine 10 and fan 11 rotatably therein.For this and other purposes, a circumferential row of hollow struts 18are welded or otherwise suitably secured in the duct, and secured attheir inner extremities to an exhaust bullet 19. Turbine 10 is rotatablymounted in suitable bearings (not shown) in the exhaust bullet. Thestructure thus far described is conventional, and no further detaileddescription is believed necessary.

In order to carry out my invention in a preferred embodiment thereof, Iprovide an annular dividing partition generally designated .24, todivide the fluid streams exhausted from ducts 2 and 3 into central andsupplementary combustion passages 25 and 26, respectively. Rather thanbeing a single wall member, partition 24 comprises inner and outerradially spaced annular walls 27 and 28, respectively, enclosing anannular fuel-vapor izing chamber 29. The walls are joined at a common 3downstream end 30, and upstream ends 31 and 32 thereof. In order tosupport the partition concentrically Within duct 13, upstream ends 31and 32 are welded .or otherwise suitably secured to struts v18. Thewalls are extended upstream in close proximity to shroud ring 12, todivide the fluid streams received from conduits 2 and 3.

Fuel is injected into chamber 29 by means of suitable nozzles 34, whichare supplied with fuel through one or more tubes 35 passing through oneor more of hollow struts 18 to the exterior of duct 13. Any desirednumber of nozzles 34 may be spaced about chamber 29, to establish adesired degree of uniformity of fuel distribution. Fuel injected intothe chamber vaporizes by abso'rbing heat from walls 27 and 28, and thisprocess of evaporation cools the interior surfaces of the walls.

As shown in Figs. 1 and 2, chamber 29 is divided into concentricsegmental portions by means of an annular baflie element 36, in order toprevent differences in pressure in passages 26 and 27 from causing animbalance in the desired division of fuel supply between them, with aresulting starvation" of one passage. The chamber is also divided intoarcuate segmental portions by means of radial baflle elements 37 and 38.At least one fuel nozzle 34 is provided for each division of thechamber. 7

In order to inject vaporized fuel evenly into passages 25 and 26, and tocool the exterior surfaces of walls 27 and 28, I form the walls with aplurality of axiallyspaced rows of circumferentially-extending louvres39, having upstream surfaces 40 which are inclined downstream from aradial inclination, and downstream surfaces 41 extending generally inradial planes. A plurality of fuel orifices 42 are circumferentiallyspaced about surfaces 41, and serve to inject vaporized fuel generallyparallel to walls 27 and 28, into passages 25 and 26, at spacedintervals along the passages. As shown by the direction of the arrows inFig. l, vaporized fuel injected into the passages sweeps over and coolsthe external surfaces of the walls, and is deflected toward the centersof the passages by successive downstream surfaces 40, to promoteeffective mixing with working fluid flowing therein. The working fluidstream in central passage 25 comprises hot combustion products, whichautomatically ignite the fuel injected therein. In supplementary passage26, combustion of fuel is initiated by means of one or morecircumferentially-spaced conventional ignitors 43, and one or more pilotfuel injection nozzles 44.

A modified form of partition 48 is shown in Fig. 3, havingcircumferential rows of individual tetrahedral louvres 49 struck up fromthe surfaces of walls 27' and 28'. Louvres 49 are formed with inclinedupstream surfaces 50 and generally radially-extending downstreamsurfaces 51, the latter being provided with fuel injection orifices 52.The partition functions in essentially the same manner as that of Figs.land 2. The baflle elements shown are similar, and are similarlynumbered, with prime superscripts.

Referring to Fig. 4, a modification in which diluent fluid is drawn fromthe by-pass fluid conduit is shown. Parts similar to those of theembodiment of Fig. l are similarly numbered, with double primesuperscripts. In this,modification, end 31" of inner wall 27" ofpartition 24" is extended upstream in close proximity to shroud ring12", and end 32" of outer wall 28" is terminated in the region of struts18". An opening 56 is thus formed to admit working fluid to chamber 29"from the bypass conduit. This arrangement provides diluent air to aid infuel evaporation and may be utilized to prevent carbonization of thenozzles 34, or in applications in which complete evaporation cannot beachieved within chamber 29" through absorption of heat by the fuelstream from walls 27" and 28" alone. The pressure in the bypass fluidconduit must be higher than that 4 I in the main fluid conduit, in orderto insure flow of vaporized fuel ms both conduits. In the event that thepressure in the main conduit is .the higher, diluent fluid may be drawntherefrom by terminating end 31" of wall 27'. in the region of strutsl8", and extending wall 28" upstream. However, the latter arrangementshould not be used in applications for which the main fluid stream is ata fuel-igniting temperature, because of the danger of ignition inchamber 29". Therefore, an additional ignitor should be provided withinpassage 25" in applications suitable for the latter arrangement.Alternatively, compressed air may be bled from themgine compressor (notshown) and supplied to chamber 29" through suitable conduit means (notshown) for the purpose of preventing carbonization of fuel nozzles 34. I

It will be apparent from the foregoing description that I have providedan improved concentric combustion system which utilizes the evaporationof fuel in a new manner to cool a hollow dividing partition internallyand externally. My improved system extends the useful life of thepartition, situated between high temperature combustion passages, byproviding effective cooling of all surfaces of the partition.

While I have shown and described particular embodiments of my invention,it will be obvious to those skilled in the art that variousmodifications may be made without departing from the spirit and scope ofthe invention,

What I claim and desire to secure by Letters Patent of the United Statesis:

1. In a ducted fan type turbine engine including an afterburner, aconcentric fuel combustion system comprising, in combination; acylindrical duct, an annular partition concentrically spaced within saidduct to divide and maintain the separation of the fluid exhausted bysaid turbine from the working fluidexhausted by said fan, said partitionincluding a pair of concentric radially spaced-apart cylindrical wallsenclosing an annular fuelvaporizing chamber, and means for supplyingstreams of fuel to said chamber, said walls each being formed with aplurality of spaced-apart orifices for injection of vaporized fuel intosaid passages from said chamber, such that said walls are cooledinternally by vaporization of fuel and cooled externally by vaporizedfuel injected into said passages through said orifices.

2. A concentric fuel combustion system as recited in claim 1, togetherwith baflie elements mounted on said walls within said "chamber todivide said chamber into segmental portions each communicating with theorifices of only one of said walls.

3. A concentric fuel combustion system as recited in claim 1, said wallsfurther forming an opening at an upstream end of said chamber forreceiving said fluid exhausted by said turbine.

4. In a ducted fan type turbine engine including an afterburner, aconcentric fuel combustion system comprising, in combination; acylindrical duct, an annular partition concentrically spaced within saidduct to divide and maintain the separation of the fluid'exhausted bysaid turbine from the working fluid exhausted by said fan, saidpartition including a pair of concentric radially spaced-apart annularwalls enclosing an annular fuelvaporizing chamber, and means forinjecting streams of fuel into said chamber for vaporization by saidfluid to cool said walls in said chamber, said walls each being formedwith a plurality of spaced-apart orificesfor injection of vaporized fuelinto said passages from said chamber for cooling said walls in saidpassages and. for combustion therein. 1

5. A concentric fuel combustion system adapted to receiveconcentricstreams of working fluid from a jetpropulsion engine of the kind havingconcentric main and bypass fluid conduits, said combustion systemcomprising, in combination; a cylindrical duct, an annular partitionconcentrically spaced within said duct to form a central combustionpassage and a divided supplementary combustion passage concentricallywithin said duct, said passages adapted to receive the streams ofworking fluid from the main and bypass conduits, respectively, saidpartition including a pair of concentric radially spacedapartcylindrical walls enclosing an annular fuel-vaporizing chamber, meansfor injecting streams of fuel into said chamber for vaporization thereinto cool said walls in said chamber, said walls each being formed with aplurality of axially spaced-apart circumferential rows of orifices forinjection of vaporized fuel into said passages from said chamber forcooling said walls in said passages and for combustion therein, and fuelignition means in said supplementary combustion passage.

6. A concentric fuel combustion system as recited in claim 4, togetherwith baflie elements mounted on said 6 walls within said chamber todivide said chamber intosegmented portions each communicating with theorifices of only one of said walls.

7. A concentric fuel combustion system as recited in.

claim 5, said walls further forming an opening at an upstream end ofsaid chamber for receiving a stream of fluid from the engine forvaporization of the streams of fuel in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS

